Low gloss weatherable polymer composition

ABSTRACT

A polymer composition comprising a blend of (a) a grafted olefin rubber, (b) an ungrafted olefin rubber, (c) a copolymeric matrix and an optional (d) a grafted acrylate rubber is disclosed. The composition which is characterized in having a desirable balance of impact strength and low gloss is useful for molding and extrusion of articles for certain outdoor applications.

BACKGROUND OF THE INVENTION

Grafted rubber compositions are well known in the art.Poly(acrylonitrile butadiene styrene) or ABS is widely known and used asa molding and extrusion composition. In ABS, polybutadiene is graftedwith acrylonitrile and styrene. For outdoor applications where thepolymer composition is exposed to sunlight and weather, a saturatedrubber such as polybutyl acrylate (PBA) polyethylene propylene (EP) orpolyethylene propylene diene monomer (EPDM) is used in place of thebutadiene used in ABS. Blends of these grafted saturated rubbers arealso known.

1. Field of the Invention

The present invention is directed to a polymer composition which is ablend of (a) an olefin rubber such as ethylene propylene diene monomerrubber grafted with styrene and acrylonitrile (EPDM-g-SAN); (b) anungrafted olefin rubber such as ethylene propylene diene monomer rubber(EPDM); (c) a poly(acrylonitrile styrene) matrix; and (d) optionally abutyl acrylate rubber grafted with styrene and acrylonitrile. Thesepolymer compositions have a desirable balance of low gloss and impactstrength which makes them especially suitable as molding and extrusioncompounds for certain outdoor applications.

2. Description of Related Art

Butyl acrylate rubber and EPDM rubbers grafted with styrene andacrylonitrile are well known in the art. Such compositions are taught inU.S. Pat. No. 3,489,822 (Witt et al); U.S. Pat. No. 4,127,617(Arrighetti et al); U.S. Pat. No. 4,145,378 (Arrighetti et al); and U.S.Pat. No. 4,912,162 (Kishida et al). Blends of a butyl acrylate rubbergrafted with styrene and acrylonitrile (BA-g-SAN) and an EP or EPDMrubber grafted with styrene and acrylonitrile (EP-g-SAN or EPDM-g-SAN)are also well known and are taught in U.S. Pat. No. 4,877,826 (Beyer);U.S. Pat. No. 4,946,894 (Henton et al) and U.S. Pat. No. 5,112,895 (C.J. Chen and F. M. Peng).

SUMMARY OF THE INVENTION

The present invention is directed to molding and extrusion compositionswhich have low sheet gloss (less than 50 preferably less than 40 at a60° angle) and good Izod impact (greater than 50 J/m). The compositionscomprise (a) an olefin rubber grafted with a vinyl aromatic monomer andan unsaturated nitrile monomer and optionally one or more compatiblecomonomers; (b) an ungrafted olefin rubber; (c) an SAN matrix polymer;and (d) optionally an acrylate rubber grafted with vinyl aromaticmonomer and an unsaturated nitrile monomer and optionally one or morecompatible comonomers;

The EP and EPDM rubbers used in the present invention are well known inthe art. Their description and a means for the preparation thereof havebeen disclosed in U.S. Pat. No. 3,489,821 and U.S. Pat. No. 4,202,948,both of which teachings are incorporated herein by reference. While avariety of alpha mono-olefins may be used in preparing EPDM rubbers,most desirably are those elastomers comprising a terpolymer of ethyleneand propylene with an ethylenically unsaturated copolymerizablenon-conjugated diene monomer. Illustrative non-limiting examples ofsuitable diene which may be used include dicyclopentadiene, ethylidenenorbornene and 1,4-hexadiene.

Methods of preparing EPDM graft copolymers are also well known in theart. The graft copolymer is polymerized in the presence of the rubberyEPDM polymer utilizing either emulsion, suspension or solutionpolymerization techniques. Examples of EPDM graft copolymers are taughtin U.S. Pat. Nos. 3,489,821, 3,489,822, 3,642,950 and 4,314,041 all ofwhich are incorporated herein by reference. Preferred grafted EPDMrubbers have a weight average particle size from 0.1 μ to 1.0 μ. Mostpreferred are those rubbers prepared by grafting the rubber spine in asolution or suspension process having a particle size of from 0.3 μ to0.6 μ.

Acrylate rubbers for use in the present invention are well known in theart and described, for example, in U.S. Pat. Nos. 3,830,878; 4,341,883;3,944,631; 3691,260 and 4,224,419, the teachings of which areincorporated herein by reference. Preferred acrylate rubbers arecrosslinked homopolymers of C₁₋₈ alkyl acrylates, especially butylacrylate or 2-ethylhexyl acrylate, and crosslinked copolymers thereofwith up to about 25 weight percent, preferably up to about 10 percent,of a copolymerizable comonomer. Suitable copolymerizable comonomersinclude monovinylidene aromatic monomers, e.g. styrene, alpha-methylstyrene, etc., acrylonitrile and alkyl methylacrylates such as methylmethacrylate. A preferred acrylate rubber comprises butyl acrylateoptionally containing various di-and tri-vinyl substituted crosslinkingand graft enhancing agents present in an amount up to about 5 percent byweight based on total rubber weight.

Preferably the acrylate rubber is prepared by an emulsion process.Emulsion polymerized acrylate rubbers may be partially agglomerated asis known in the art in order to provide a greater variety of particlesize distribution in the resulting acrylate rubber product therebycontrolling gloss and impact properties of the polymer. The rubberparticles can also be grown to various sizes by varying thepolymerization conditions and/or a mixture of previously prepared largeand small seed particles may be employed to form the grafted rubber. Thegrafted acrylate rubber's weight average particle diameter is preferablyfrom about 0.05 μ to about 0.5 μ, most preferably from 0.1 μ to 0.25 μ.Particle diameters are measured in the latex form of the rubber beforegrafting using techniques of transmission Electron Microscopy orhydrodynamic chromatography as disclosed in U.S. Pat. No. 4,419,496.Grafting of acrylate rubbers is also well known in the art and isdisclosed, for example, in the above cited U.S. Pat. Nos. 3,830,878;4,341,893; 3,944,631; 3,691,260 and 4,224,419. Preferably thecrosslinked acrylate rubber is grafted by means of an emulsion process.

The amount of grafting in both the EPDM and acrylate rubbers may varyover a wide range. As defined by percent grafting (attached rigid phaseweight/rubber weight×100) the percent graft may be from about 5 to about150. Preferred percent grafting limits are from about 10 to 100.Desirable grafting levels are dependent on particle sizes. Large rubberparticles generally possess lesser amounts of graft copolymer on apercentage basis. While it is preferred that each rubber substrate begrafted with a graft copolymer which is similar to the matrix resin,different copolymers may be employed for the various graft copolymersand matrix copolymer provided that these different copolymers aremutually compatible.

The matrix copolymer is typically prepared during the polymerizationprocesses used to graft the EPDM and acrylate elastomers. Preferred arematrix copolymers comprising from 60 to 90% vinyl aromatic monomer, 10to 40% nitrile monomer and 0 to 20 percent by weight of an acrylate,e.g. methylmethacrylate. More preferred matrix copolymers comprise 65 to80% by weight styrene, 20 to 35% by weight acrylonitrile and 0 to 20% byweight of methylmethacrylate.

In addition to the matrix polymer formed during the grafting process,additional separately prepared compatible matrix polymer may be added tothe compositions of this invention. Separately prepared matrix may bethe same or different from the above described matrix formed during thegrafting step.

The total amount of rubber in the blends is in the range of from 5 to30% by weight based on the total weight of components (a), (b), (c) and(d). Preferably, when component (d) is not included, the total amount ofrubber in the blend is in the range of from about 20 to about 30% byweight based on the total weight of components (a), (b) and (c). Whenall four components are present, the preferred amount of rubber is inthe range of from about 10 to about 30% by weight.

By means of an appropriate selection of the rubber particle size, amountof crosslinking and the total amount of EPDM and acrylate rubber used inthe polyblend, compositions having a wide variety of product propertiesmay be prepared.

Stabilizers such as antioxidants and ultraviolet absorbers and hinderedamine light stabilizers can also be added to the present compositions.Examples of antioxidants include the hindered phenolics, thioesters,phosphates and amine antioxidants. Suitable U.V. active stabilizersinclude the aromatic ketones, hydroxy ketones and esters, as well asother species that have U.V. absorption capability. Suitable hinderedamine light stabilizers include Tinuvin 144, Tinuvin 770 and Cyasorb UV3346. Flow aids, plasticizers, and lubricants can also be added to thepresent invention.

Having described in invention of the following examples are provided asfurther illustrative and are not to be construed as limiting.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The ungrafted EPDM component used in the working examples was RoyaleneIM-7100 supplied by Uniroyal Chemical Company.

The EPDM-g-SAN used in the working examples was Royaltuf 372 supplied byUniroyal Chemical Company. It is further characterized as containing 50by weight of EPDM rubber which is grafted with SAN in a S/AN weightratio of 72/28. Other suitable EPDM and girfted EPDM rubbers are wellknown to those of ordinary skill in the art.

The separately prepared SAN matrix used was a copolymer containing about68% by weight of styrene and about 32% by weight of acrylonitrile basedon the total weight of the SAN copolymer.

The butylacrylate rubber grafted with styrene and acrylonitrile(BA-g-SAN) was prepared by polymerizing butyl acrylate to form apolybutylacrylate rubber using conventional emulsion polymerization. Therubber was crosslinked during polymerization such that the swellingindex of the rubber in methyl ethyl ketone at 25° C. was about 10. Therubber was grafted by polymerizing a 70/30 weight ratio of styrene andacrylonitrile (120 parts total) in the presence of 100 parts of therubber. The resulting grafted rubber had a weight average particle sizediameter (Dw) of about 0.2 microns with a range of from about 0.08 toabout 0.4 microns. The grafted rubber contained about 45% by weight ofbutyl acrylate and about 55S by weight of styrene acrylonitrilecopolymer (SAN) present as grafted polymer and as free ungrafted matrixcopolymer formed during the graft polymerization procedure.

Test Methods

1. Inverted Dart Impact (IDI)—A dart with a hemispherical head having adiameter of 0.013 meter was used, against which the specimen was drivenat a constant speed of 3.39 meters/second. This is in accordance withthe procedure set forth in ASTM D-3763 (specimen thickness was 2.54 mm,ring diameter was 31.75 mm). Results are expressed in Joules.

2. Izod Impact (J/m)—A falling pendulum with 163 Joules of energy at avelocity of 3.5 meters per second strikes a fixed specimen. The heightof the pendulum swing after striking is a measure of the energy absorbedand thus indicates impact strength. Results are expressed inJoules/meter. This is in accordance with the procedures set forth inASTM D-256.

3. Gloss was measured at 60 degrees using a Pacific ScientificGloss-Grad II glossmeter. The ASTM D-523 procedure for specular glosswas used. To obtain the average gloss value, measurements were takenfrom three locations on an extruded sheet which measured 9.16 cm×59.96cm.

Sample Preparation

The grafted and ungrafted rubber components, the SAN copolymer andadditives were melt compounded using a Banbury Mixer followed bypelletizing. The resulting pellets were then molded and tested for Izodand IDI strength properties. For gloss measurement, the pellets wereextruded into a 0.127 cm sheet using a 2.54 cm single screw extruder at230° C.

EXAMPLES 1 TO 9

These examples are based on a blend of (a) an EPDM-g-SAN which contains50% by weight of EPDM based on the total weight of the EPDM-g-SAN; (b)ungrafted EPDM; and (c) SAN matrix. The total amount of rubber in theexamples varies from 25% by weight based on the total weight of (a), (b)and (c) in Examples 1 to 5 to 15% by weight in Examples 8 and 9. Theresults of the tests on these Examples are tabulated in Table I below.

TABLE I SUMMARY OF EXAMPLES 1 TO 9 Example (1) 1 2 3 4 5 6 7 8 9 EPDM 06.25 12.5 18.75 25 0 10 0 7.5 EPDM-g-SAN 50 37.5 25.0 13.5 0 40 20 3015.0 SAN 50 56.25 62.5 67.75 75 60 70 70 77.5 % Rubber EPDM 0 6.25 12.518.75 25 0 10 0 7.5 EPDM-g-SAN 25 18.75 12.5 6.25 0 20 10 15 7.5 Ratio(2) 0/25 1/3 1/1 3/1 25/0 0/20 1/1 0/15 1/1 Total Rubber 25 25 25 25 2520 20 15 15 Gloss 71 28 23 24 * 68 37 75 60 IDI, 23° C. Emax (J) 17.413.1 6.7 1.2 0.6 17.8 5.0 18.4 2.1 Efail (J) 26.1 15.4 6.9 1.2 0.6 24.25.2 25.5 2.2 Izod, 23° C. 1.27 × 0.32 cm (J/m) 418.8 302.9 57.9 26.1 9.1193.1 43.1 73.8 34.5 1.27 × 1.27 cm (J/m) 513.1 244.4 59.5 28.2 11.0234.6 51.6 142.4 41.0 (1) % by weight of components (a), (b) and (c) (2)Ratio of % rubber in EPDM/% rubber in EPDM-g-SAN *Sheet surface was verypoor (rough surface).

Referring to Table I, Control Examples 1, 6 and 8 which do not containan EPDM component have gloss values over 50. Control Example 5 which didnot contain an EPDM-g-SAN component had a very poor surface. Examples 2and 3 illustrate that at 25% by weight of total rubber and a weightratio of EPDM/EPDM-g-SAN in the range of from 1/3 to 1/1 a material witha gloss less than 50 is obtained with an Izod impact greater than 50J/m. Example 7, which contains 20% by weight of total rubber and anEPDM/EPDM-g-SAN weight ratio of 1/1 has low gloss (37) and an Izod of51.6 J/m for the 1.27×1.27 cm sample. In Example 4, the weight ratio is3/1 and in Izod values are low (26.1 and 28.2). In Example 9, the totalamount of rubber is 15% by weight and the gloss is 60 and the Izodvalues are 34.5 and 41.0.

Examples 1 to 9 demonstrate that when using components (a), (b) and (c)without component (d) the total amount of rubber should be in the rangeof greater than 15% to about 30% and the weight ratio of EPDM/EPDM-g-SANshould be in the range of from about 3/1 to about 1/1.

EXAMPLES 10 TO 14

In these Examples, four component blends were prepared and tested asdescribed above. The forth component is a butyl acrylate rubber which isgrafted with a styrene acrylonitrile polymer (EA-g-SAN). The amount ofbutyl acrylate rubber in the BA-g-SAN component is 45% by weight basedon the total weight of the BA-g-SAN. The EPDM-g-SAN component contains50% by weight of EPDM based on the total weight of the EPDM-g-SAN. Theresults of the tests are tabulated in TABLE II below.

TABLE II SUMMARY OF EXAMPLES 10 TO 16 Example (1) 10 11 12 13 14 15 16EPDM 10 8.75 7.5 5.0 2.5 5.8 0 EPDM-g-SAN 0 2.5 5.0 10.0 15.0 23.4 20SAN 56.7 55.45 54.2 51.7 49.2 54.1 46.7 BA-g-SAN 33.3 33.3 33.3 33.333.3 16.7 33.3 % Rubber EPDM 10 8.75 7.5 5.0 2.5 5.8 0 EPDM-g-SAN 0 1.252.5 5.0 7.5 11.7 10 BA-g-SAN 15 15 15 15 15 7.5 15 Ratio (2) 10/0 7/13/1 1/1 1/3 1/2 0/10 Total Rubber 25 25 25 25 25 25 25 Gloss * * 20 2339 25 81 IDI, 23° C. Emax. (J) 1.6 2.5 10.5 18.2 17.6 16.0 19.5 Efail(J) 1.7 3.4 12.6 29.4 34.1 26.5 31.7 Izod, 23° C. 1.27 × 0.32 cm (J/m)47.3 43.2 63.8 162.9 352.2 231.1 224.0 1.27 × 1.27 cm (J/m) 47.2 45.262.2 124.8 179.7 128.6 216.8 (1) % by weight of components (a), (b), (c)and (d) (2) ratio of % rubber in EPDM/% rubber in EPDM-g-SAN *Sheetsurface was very poor (rough surface)

Referring to Table II, Example 16, which illustrates the prior artcompositions of BA-g-SAN and EPDM-g-SAN, has an Izod value of 216.8 butvery high gloss level (81).

Example 10, which does not contain an EPDM-g-SAN component, has an Izodvalue of 47.2 and a very poor sheet surface appearance. In Examples 11to 13, a portion of the EPDM rubber is replaced with EPDM-g-SAN. Atlevels of 1.25 parts of EPDM-g-SAN and 8.75 parts for EPDM (Example 11)the sheet surface appearance is poor and the Izod is 45.2. In Examples12 and 13 the use of 2.5 and 5.0 parts of rubber from EPDM-g-SANrespectively provides a sheet with a good surface appearance and lowgloss (20 and 23) and the Izod values increase to 62.2 and 124.8respectively.

Examples 12 to 15 illustrate that when component (d) EA-g-SAN is presentand the total weight percent of rubber is at 25%, the weight ratio ofrubber in the EPDM and EPDM-g-SAN components may range from about 3/1 toabout 1/3 and the resulting compositions still have a gloss below 50 andan Izod impact greater than 50 J/m.

The polyblends of the present invention may suitably be blended withother polymers to prepare useful molding resins. Examples of suitableother polymers are ABS, polycarbonates, polyaryl ethers, polysulfones,polyvinyl chloride, polymethylmethacrylate and the like.

What is claimed is:
 1. A composition comprising: (a) an olefin rubbergrafted with a vinyl aromatic monomer and an unsaturated nitrile monomerand optionally one or more compatible comonomers; (b) an ungraftedolefin rubber selected from the group consisting of EP rubbers and EPDMrubbers; (c) a matrix polymer prepared from a vinyl aromatic monomer andan unsaturated nitrile monomer and optionally one or more compatiblemonomers; and (d) optionally an acrylate rubber grafted with a vinylaromatic monomer and an unsaturated nitrile monomer and optionally oneor more compatible comonomers; wherein (c) is present in an amount of49.2 to 70 percent relative to the weight of the composition and thetotal amount of rubber in the composition is in the range of from about20% to about 30% by weight based on the total weight of the compositionand wherein the weight ratio of the amount of rubber in component (b)and component (a) is in the range of from 1/3 to 1/1 with the provisothat when component (d) is present in the composition then the weightratio of the amount of rubber in component (b) and component (a) is inthe range of from 1/3 to 3/1 and the total amount of rubber in thecomposition is from about 5% to about 30% by weight and wherein thecomposition has a gloss value of less than 50 as determined by ASTMD-523 and an Izod impact value at 23° C. of greater than 50 J/m asdetermined on a sample 1.27 cm×1.27 cm as determined by ASTM D-256.
 2. Acomposition as in claim 1 wherein component (a) is an EPDM rubbergrafted with styrene and acrylonitrile.
 3. A composition as in claim 1wherein component (c) is a SAN copolymer containing from 5 to 40% byweight of acrylonitrile (AN).
 4. A composition as in claim 3 whichfurther contains a butyl acrylate rubber grafted with styrene andacrylonitrile and wherein from 2.5 to 25% by weight of the total rubberin the composition is butyl acrylate rubber.
 5. A composition as inclaim 2 wherein from 90 to 60 weight percent of styrene and from 10 to40 weight percent of acrylonitrile based on the total weight of styreneand acrylonitrile is used in the graft on component (a).
 6. Acomposition comprising: (a) an olefin rubber grafted with a vinylaromatic monomer and an unsaturated nitrile monomer and optionally oneor more compatible comonomers; (b) an ungrafted olefin rubber selectedfrom the group consisting of EP rubbers and EPDM rubbers; and (c) amatrix polymer prepared from a vinyl aromatic monomer and an unsaturatednitrile monomer and optionally one or more compatible monomers; wherein(c) is present in an amount of 49.2 to 70 percent relative to the weightof the composition and the total amount of rubber in the composition isin the range of from about 20% to about 30% by weight based on the totalweight of the composition and wherein the weight ratio of the amount ofrubber in component (b) and component (a) is in the range of from 1/3 to1/1 wherein the composition has a gloss value of less than 50 asdetermined by ASTM D-523 and an Izod impact value at 23° C. of greaterthan 50 J/m as determined on a sample 1.27 cm×1.27 cm as determined byASTM D-256.
 7. A composition as in claim 6 where the olefin rubber usedin component (a) is selected from the group consisting of EP and EPDMrubbers.
 8. A composition comprising: (a) an ethylene propylene dienemonomer rubber grafted with a vinyl aromatic monomer and an unsaturatednitrile monomer and optionally one or more compatible comonomers; (b) anungrafted ethylene propylene diene monomer rubber; (c) a matrix polymerprepared from a vinyl aromatic monomer and an unsaturated nitrilemonomer and optionally one or more compatible monomers; and (d) a butylacrylate rubber grafted with a vinyl aromatic monomer and an unsaturatednitrile monomer and optionally one or more compatible comonomers;wherein (c) is present in an amount of 49.2 to 70 percent relative tothe weight of the composition and the weight ratio of the amount ofrubber in component (b) and component (a) is in the range of from 1/3 to3/1 and the total amount of rubber in the composition is from about 5%to about 30% by weight and wherein the composition has a gloss value ofless than 50 as determined by ASTM D-523 and an Izod impact value at 23°C. of greater than 50 J/m as determined on a sample 1.27 cm×1.27 cm asdetermined by ASTM D-256.